Gas and Oil Home Heating Furnaces - Oil burner kicks on even with elec hot water heater

Our house has an oil burner/hot water setup, plus a 40 gal electric hot water heater. It's great getting in the shower and having immediate hot water, but whether it's in the shower or doing the dishes, the oil burner comes on within 1 minute or so. I figured the elec hot water heater would provide all the water, at least more then a couple gallons worth before the oil burner kicked on. Seems like a waste to have both. I've tried turning the oil burner off this summer, but it started leaking water. No go there.
Anyways, seems like a waste to use electricity to keep the hot water in the heater warm and also to use oil to run the oil burner, when we really don't need it running till the winter. Any thoughts?

I suspect your domestic water first goes thru the domestic coil on the boiler then to the electric tank. If this is the case, what you are experiencing is perfectly normal. As cold water flows thru the coil, it drops the boiler temperature & causes the burner to fire. If the water, after it passes thru the boiler is hot enough, the electric won't kick in except to maintain temperature.

Thanks for the explanation. Makes sense.